The vocabulary around gender is a fairly tricky part of discussing these issues today. Pronouns, for example, can get difficult when someone doesn't identify as male or female. Do you refer to them as they instead of he or she, or use one of the invented pronouns like ne, ve, ey, ze, or xe? (Generally, the advice from LGBTQ groups is to just ask and use what people prefer.)

Javier Zarracina/Vox

But how do you refer to an uncle or aunt if they identify as genderqueer — so male or female don't necessarily apply to them? Or niece and nephew? These are issues that we just don't have good answers to, but will likely get worked out eventually. After all, language is hugely adaptive and changing all the time.

So Merriam-Webster's additions show the vocabulary we use for gender is changing, but there's still a lot more change likely to come.